Electronically controlled fuel injection system

ABSTRACT

An electronically controlled fuel injection system comprising a plurality of fuel supply systems one of which is connected with a part of fuel injection valves and the other is connected with the rest of the fuel injection valves, wherein one fuel supply system supplies fuel of lower pressure than the other thereby enabling the engine to operate with lean mixture for reducing harmful components in the exhaust gas of the engine.

United States Patent 1191 1 1 3,910,241 Fujisawa et al. Oct. 7, 1975 [5ELECTRONICALLY CONTROLLED FUEL 3,738,341 6/1973 Loos .7 123/32 EAINJECTION SYSTEM 3,745,768 7/1973 Zechnall et al... l23/l40 MC u3,827,237 8/1974 Linder et al. 60/301 Inventors: HIdeya Flulsawa; Normboth 3,851,632 12/1974 Teshirogi et al. 60/276 of Kariya, Japan [73]Assignee: Nippondenso Co., Ltd., Japan Primary Examiner-Charles J. MyhreAssistant Examiner-Paul Devinsky [22] [Med 1974 Attorney, Agent, orFirmCushman, Darby & [21] Appl. No.: 495,125 Cushman Forelgn ApplicationPrlority Data ABSTRACT Aug. 11, 1973 Japan 48-90299 An electronicallycontrolled fuel injection system [52] US. Cl. 123/32 EA; 123/140 MC;/276; comprising a plurality of fuel supply systems one of 60/285 whichis connected with a part of fuel injection valves [51] Int. Cl. F02B3/00; FOZD l/06; FOlN 3/00 and the other is connected with the rest ofthe fuel in- [58] Field of Search... 123/32 EA, 32 AE, MC, jectionvalves, wherein one fuel supply system supplies 123/140 MP, 140 R;60/276, 285 fuel of lower pressure than the other thereby enabling theengine to operate with lean mixture for reducing [56] References Citedharmful components in the exhaust gas of the engine.

UNITED STATES PATENTS 4 Cl 7 D F 3,576,182 4/1971 Howland 123/140 MC r sl US. Patent Oct. 7,1975 Sheet 2 of5 3,910,241

Sheet 3 of5 3,910,241

US Patent 0m. 7,1975

US. Patent Oct. 7,1975 Sheet 4 of5 3,910,241

US. Patent Oct. 7,1975 Sheet 5 of5 3,910,241

bl w m m m m m 2 .5 3 523 t 238 6E 201530 5 3 vs 221 E L ELECTRONICALLYCONTROLLED FUEL INJECTION SYSTEM BACKGROUND OF THE INVENTION v Thisinvention relates to an improvement of an electronically controlled fuelinjection system which is equipped with an oxygen content detector inthe exhaust system to control the fuel injection in accordance with theoxygen content in the exhaust system, thereby reducing harmfulcomponents in the exhaust gas. The amount of oxygen in the exhaust gasvaries with the value of air-fuel ratio as shown in FIG. 1 which theoxygen content detector detects to produce an electromotive force thecharacteristics of which has a peculiar point, as shown in FIG. 2, atthe air-fuel ratio of about 14.8 which corresponds to the begining ofoxygen curve in FIG. 1. The oxygen content detector has been well knownfrom the early days. It was developed at first as a simple oxygendetector for general use and then it was utilized in an exhaust gaspurifying system to detect the oxygen content in the exhaust gas,thereby controlling the air-fuel ratio at the intake system. Thedetector is made of such metal oxide as Zirconium dioxide and Titaniumdioxide. The metal oxide becomes electrolytic when it is heated and itgenerates electromotive force when there is a difference of oxygencontent between one side thereof and the other by the movement of oxygenion.

In a conventional fuel injection system mounting such oxygen contentdetector, the air-fuel ratio can be controlled at no other value than14.8. Because the detector applies the control signal generated thereinto a computor, which operates to modify the injection pulse inaccordance with the signal. The pulse modification is made by such a waythat the air-fuel ratio always meets a value of about 14.8 to increasethe fuel when the ratio is above 14.8 and decrease when below 14.8,thereby holding the value of about 14.8 continuously. At the point ofabout 14.8, the electromotive force of the detector changes abruptly asseen from FIG. 2, enabling the electrical treatment easy, although atthe other points, the change rate of the output is not big, causingcomplexity of treatment.-

SUMMARY OF THE INVENTION With a view to overcome the problem describedabove, it is the primary object of the present invention to provide anelectronically controlled fuel injection system which can control totalair-fuel ratio to be set in the range which is different from the rangeof around 14.8 thereby to reduce harmful components in the exhaust gasof the engine more effectively. For example if the ratio is set at about18.5, lower level of CO, BC and NOx emission can be obtained. It is thefurther object of the invention to provide a plurality of fuel supplysystems in the fuel injection system with relatively simple constructionand low cost.

The above and other objects, features and advantages of the presentinvention will be apparent from the following detailed description ofpreferred embodiments taken in conjunction with the accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 shows a graph representing therelation between air-fuel ratio and two typical components in theexhaust gas.

FIG. 2 shows a graph representing the relation between air-fuel ratioand electromotive force generated in the oxygen content detector.

FIG. 3 shows a schematic plan view of the electronically controlled fuelinjection system of the present invention.

FIG. 4 shows an electric diagram of computer of the fuel injectionsystem of the present invention.

FIG. 5 shows an enlarged cross sectional view of fuel pressure regulatorof the fuel injection system of the present invention.

FIG. 6 shows another embodiment of fuel supply system of the fuelinjection system of the present invention.

FIG. 7 shows a graph representing the relation between air-fuel ratioand fuel pressure in' the fuel supply system of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT manifold, 17 a second exhaustmanifold, 19 an oxygen content detector. The computer 1 controls toenergize the fuel injection valves 2 and 3 during suitable time periodto inject suitable amount of fuel into an engine 21 in response to thesignals from a vacuum pressure detector 23, crankshaft turning angledetector 25 and oxygen content detector 19. The angle detector 25 closestimes per 1 engine cycle to inject the fuel simultaneously into everycylinders of the engine 21 2 times per one engine cycle from the fuelinjection valves 2-and 3. The first fuel pressure regulator 9 regulatesthe pressure of the fuel discharged from the fuel pump 7 to supplyconstant pressure fuel to the fuel injection valve 2 which is mounted onthe leftmost cylinder of the engine 21. The oxygen content detector 19is mounted on the first exhaust manifold 15 which is connected with thesaid leftmost cylinder. The first fuel pressure regulator 9 is suchconstruction as shown in FIG. 5, in which a diaphragm 27 is installed ina casing 29 with avalve seat 32 to divide the inner chamber into anupper and a lower chambers 31 and 33, and a coil spring 35 is installedin the lower chamber 33, and a projecting pipe 37 is installed in thechamber 31 with a valve portion 39 which faces the valve seat 32. Theupper chamber 31 is connected with the fuel pump 7 through a fuel pipe41 and the fuel injection valve 2 through a fuel pipe 43 thereby tointroduce the fuel discharged from the fuel pump 7 and discharge it tothe fuel injection valve 2.

The projecting pipe 37 is connected with the fuel tank 5 through a fuelpipe 45 to discharge the fuel from the upper chamber 31 to the fuel tankwhen the fuel pressure goes up to push the diaphragm 27 downward toseparate the valve seat 32 from the valve portion 39.

The lower chamber 33 is connected with an intake pipe 47 of the engine21 through a vacuum pressure pipe 49 to lead the vacuum pressureproduced in the intake pipe 47 thereto. Therefore, the diaphragm 27together with the valve seat 32 moves in response to the fuel pressureand vacuum pressure to control the fuel amount returning to the fueltank from the upper chamber 31, thus regulating the fuel pressure. The

pressure of the fuel depends on the characteristic of the coil spring 35as well.

The second fuel pressure regulator l 1 is similar to the said first fuelpressure regulator 9, except that the spring constant of the coil springof the second fuel pressure regulator 11 is selected smaller than thatof first fuel pressure regulator so that the second fuel pressureregulator 11 regulates the fuel pressure at a lower value than that ofthe first fuel pressure regulator 9. Therefore the lower pressure fueli.e., the less amount of the fuel is supplied by the respective fuelinjection valves 3 than that supplied by the leftmost injection valve 2,through the fuel distributor l3 and fuel pipes 51 into the cylindersequipped with the fuel injection valves 3 upon energizing both of thefuel injection valves 2 and 3 with the same time period.

As the oxygen content detector 19 transmits its signal to the computer1, the computer keeps the air-fuel ratio of the leftmost cylinder atabout 14.8, by controlling the injection time of the fuel injectionvalve 2. On the other hand, in the rest of the cylinders equipped withthe fuel injection valves 3, less fuel is injected, thus to make theair-fuel ratio larger than that of the leftmost cylinder.

A relation between air-fuel ratio and regulated fuel pressure for a4-cycle and 6-cylinder engine is exemplificd in FIG. 7, wherein theair-fuel ratio of the cylinder connected with the fuel injection valve 2is controlled at 14.8, the fuel pressure in the fuel pipe 43 isregulated at 2.55 kg/cm and the rest of the five cylinders are suppliedwith less amount of fuel respectively. As seen from FIG. 7, the totalair-fuel ratio is controlled to be almost equal to that of leancylinders connected with the fuel injection valves 3. For example, ifthe total airfuel ratio of about 18.5 is expected to eliminate harmfulcomponents in the exhaust gas, the fuel injection valves 3 should beprovided with the fuel of about 1.5 kg/cm making the air-fuel ratio ofthe cylinders connected with the valves 3 at about 19.2. Consequently,the engine 21 as a whole is operated with lean mixture, which reducesharmful components in the exhaust gas with the resultant increase of theperformance of the catalytic converter as well.

FIG. 6 is another fuel supply system, which is also available. Numeral53 designates an intermediate fuel pipe connecting a first pressureregulator 55 with a second fuel pressure regulator 57, which correspondrespectively to the aforesaid first and second fuel pressure regulators9 and 11. A fuel pipe 59 is connected with the fuel tank to returnoverflowing fuel thereto. A fuel pipe 61 is connected with the leftmostfuel injection valve 2 and a fuel pipe 63 is connected with the fuelinjection valves 3. Numeral 65 designates a fuel pump which is exactlysame to the fuel pumps 7 and 8 of the aforesaid system. A coil spring 67of the second fuel pressure regulator 57 is smaller in the springconstant than a coil spring of the first fuel pressure regulator 55 sothat the fuel injection valves 3 inject less fuel than the valve 2 inthe same manner as that of shown in FIG. 3.

Next, construction and operation of the computer 1 will be explainedwith reference to FIG. 4. Numeral 71 designates a wave shaping circuitwhile is connected with the crankshaft turning angle detector 25. Thewave shaping circuit comprises resistors 71a, 71b, 71c and 71d, acapacitor 71g, NAND circuits 71f, 71d, 7 1i and 71j, a transistor 7le.The NAND circuits 71i and 711' constitute a flip-flop circuit. When thecrankshaft turning signal is generated, the wave shaping circuit 71generates a rectangular signal which is syncronized with the crankshaftrotation. Numeral 73 is an integrating circuit which comprises resistors73a, 73b, 73d and 73f, a transistor 730, a capacitor 73e, diodes 73g and7311 and an operational amplifier 731'. The integrating circuit 73performs its integration when the output signal of the NAND circuit 71jis in the 0 state and is reset when the signal is in the 1 state.Numeral 75 is a voltage regulating circuit which comprises a resistor75a and a Zener diode 75b. The voltage regulating circuit provides theconstant voltage, which is integrated by the integrating circuit 73.Numeral 77 is a control circuit which comprises resistors 77a, 77f, 77gand 77h, operational amplifiers 77b and 771'. The operational amplifier77b amplifies the output signal of the oxygen content detector 19, whilethe other amplifier 77i adds the both output signals of the vacuumpressure detector 23 and the operational amplifier 77b. Numeral 79 is acomparator circuit comprising resistors 79a and 79b and a comparator 790with the outputconnected to the input of the NAND circuit 71j. Thecomparator produces 1" signal as its output when the output voltage ofthe integrating circuit 73 is lower than the output voltage of thecontrol circuit 77, while it produces when the former is higher than thelatter. When the comparator produces 0 signal, the NAND circuit isrendered 1 state, thereby resetting the integrating circuit 73. Numeral81 designates a driving circuit which comprises resistors 81a, 81b, 81c,81d, 81f, 81g and 811', and transistors 8le, 8111 and 8lj. The base ofthe transistor Sle is connected with the output of the NAND circuit 71When the output of the NAND circuit 71 j is in the 1" state thetransistor 81e is kept conductive and the transistors 8111 and 81j arekept nonconductive. However, once the crankshaft turning angle detector25 generates a signal, it renders the NAND circuit 71] into 1 state,thus making the transistor 8le nonconductive and the transistors 81/1and 81j conductive thereby to drive the injection valves 2 and 3.

As noted above, the fuel injection is started when the crankshaftturning angle detector 25 generates a signal and interrupted when thecomparator circuit produces a 0 signal, whereby the injection period isresponsive to the signals of vacuum pressure detector 23 and the oxygencontent detector 19, with the result that the fuel is controlled inresponse to'the vacuum pressure of the intake pipe 47 and the oxygencontent in the first exhaust manifold 15.

In this computer, the vacuum pressure detector 23 can be replaced by anair-flow meter, which is installed in the intake pipe 47.

As described above, the fuel injection system of the present inventionhas two different fuel supply systems 1 each of which supplies the fuelof different pressure engine, a computor for energizing the fuelinjection valves in response to oxygen content in the exhaust gasejected from the engine and an oxygen content detector mounted in one ofsaid exhaust manifolds of a selected number of cylinders of said enginecomprising;

a first fuel pressure regulator connected with said fuel pump and aselected number of said fuel injection valves respectively mounted onsaid selected number of cylinders for regulating the pressure of thefuel at a predetermined value to supply the regulated fuel to saidselected number of said fuel injection valves from said fuel pump and asecond fuel pressure regulator connected with said fuel pump and therest of said fuel injection valves respectively mounted on the rest ofcylinders for regulating the pressure of the fuel at anotherpredetermined value to supply the regulated fuel to said rest of saidfuel injection valves from said fuel pump.

2. In combination with an internal combustion engine having first andsecond exhaust manifolds, an electronically controlled fuel injectionsystem comprising;

a fuel pump for supplying the fuel to the system,

fuel injection valves mounted on cylinders of said engine for injectingthe fuel into said cylinders,

a computor connected with said fuel injection valves for energizing thesaid valves in response to signals representing the operating conditionsof said engine,

an oxygen content detector mounted in said first exhaust manifold ofsaid engine connected with a selected number of said cylinders to supplythe oxygen content signal to said computor as the signal representingthe operating conditions of said engine,

a first fuel pressure regulator connected with a selected number of saidfuel injection valves mounted on said selected number of said cylindersbeing led to said first exhaust manifold for regulating the fuelpressure at a predetermined value,

a second fuel pressure regulator connected with the rest of said fuelinjection valves mounted on the rest of said cylinders being let to saidsecond exhaust manifold which is separately mounted on said engine fromsaid first exhaust manifold for regulating the fuel pressure at anotherpredetermined value.

3. An electronically controlled fuel injection system as claimed inclaim 2, wherein;

said first fuel pressure regulator comprises two chambers separated by adiaphragm from each other, one of which is connected with said selectednumber of said fuel injection valves and said fuel pump and providedwith a discharge pipe for discharging the fuel therefrom and the otheris connected with an intake pipe of said engine and provided with aspring for setting the pressure of the regulated fuel at saidpredetermined value and said second fuel regulator comprises twochambers separated by a diaphragm from each other, one of which isconnected with the said rest of said fuel injection valves and said fuelpump and provided with a discharge pipe for discharging the fueltherefrom and the other is connected with said intake pipe of saidengine and provided with a spring having another spring constant forsetting the pressure of the regulated fuel at said differentpredetermined value.

4. An electronically controlled fuel injection system as claimed inclaim 3, wherein;

said second fuel pressure regulator keeps the fuel pressure at lowervalue than that of said first fuel pressure regulator, thereby makingthe total airfuel ratio larger than that of said selected number of saidcylinders combined with said first fuel pres sure regulator.

1. In combination with an internal combustion engine having at least twoexhaust manifolds, an electronically controlled fuel injection systemhaving a fuel pump for supplying fuel to the system from a fuel tank,fuel injection valves for injecting the fuel into cylinders of saidengine, a computor for energizing the fuel injection valves in responseto oxygen content in the exhaust gas ejected from the engine and anoxygen content detector mounted in one of said exhaust manifolds of aselected number of cylinders of said engine comprising; a first fuelpressure regulator connected with said fuel pump and a selected numberof said fuel injection valves respectively mounted on said selectednumber of cylinders for regulating the pressure of the fuel at apredetermined value to supply the regulated fuel to said selected numberof said fuel injection valves from said fuel pump and a second fuelpressure regulator connected with said fuel pump and the rest of saidfuel injection valves respectively mounted on the rest of cylinders forregulating the pressure of the fuel at another predetermined vaLue tosupply the regulated fuel to said rest of said fuel injection valvesfrom said fuel pump.
 2. In combination with an internal combustionengine having first and second exhaust manifolds, an electronicallycontrolled fuel injection system comprising; a fuel pump for supplyingthe fuel to the system, fuel injection valves mounted on cylinders ofsaid engine for injecting the fuel into said cylinders, a computorconnected with said fuel injection valves for energizing the said valvesin response to signals representing the operating conditions of saidengine, an oxygen content detector mounted in said first exhaustmanifold of said engine connected with a selected number of saidcylinders to supply the oxygen content signal to said computor as thesignal representing the operating conditions of said engine, a firstfuel pressure regulator connected with a selected number of said fuelinjection valves mounted on said selected number of said cylinders beingled to said first exhaust manifold for regulating the fuel pressure at apredetermined value, a second fuel pressure regulator connected with therest of said fuel injection valves mounted on the rest of said cylindersbeing let to said second exhaust manifold which is separately mounted onsaid engine from said first exhaust manifold for regulating the fuelpressure at another predetermined value.
 3. An electronically controlledfuel injection system as claimed in claim 2, wherein; said first fuelpressure regulator comprises two chambers separated by a diaphragm fromeach other, one of which is connected with said selected number of saidfuel injection valves and said fuel pump and provided with a dischargepipe for discharging the fuel therefrom and the other is connected withan intake pipe of said engine and provided with a spring for setting thepressure of the regulated fuel at said predetermined value and saidsecond fuel regulator comprises two chambers separated by a diaphragmfrom each other, one of which is connected with the said rest of saidfuel injection valves and said fuel pump and provided with a dischargepipe for discharging the fuel therefrom and the other is connected withsaid intake pipe of said engine and provided with a spring havinganother spring constant for setting the pressure of the regulated fuelat said different predetermined value.
 4. An electronically controlledfuel injection system as claimed in claim 3, wherein; said second fuelpressure regulator keeps the fuel pressure at lower value than that ofsaid first fuel pressure regulator, thereby making the total air-fuelratio larger than that of said selected number of said cylinderscombined with said first fuel pressure regulator.